Locking fixture



Patented Oct. 3, 1944 UNITED STATES PATENT oEFicE LOCKING FDTURE Guy, E.Swartz, Detroit, Mich. Application October 6, 1941, Serial No. 413,857

4 Claims.

The present invention relates to locking fixtures for use in productionof machine parts, for example, in xing parts to be subjected to multipledrilling or other operations.

In the use of such fixtures for so-called heavy duty operations, wherethe part being worked is large and requires large clamping means, it hasbeen found that the quite heavy movable member of the clamp is difficultto move up and down and consequently subjects the operator and theoperating parts to undue strains.

It is among the objects of the present invention to provide means forovercoming such diiiiculties by the use of weight compensation meansacting on the heavy clamp element.

Another object is a weight compensation means which may be adjusted bothfor tension and for considerable variation in the dimension of the partto be clamped.

Other objects and advantages will readily occur to those skilled in theart upon reference to the following description and the accompanyingdrawing in which Figure 1 is a perspective View of a locking iixtureembodying the invention.

Figure 2 is a longitudinal central vertical sectiona1 view of the baseportion.

Figure 3 is a section on line 3 3 of Figure 2.

As indicated in the drawing, a xture embodying the present invention mayconsist of a base Il) having at each end guide sleeves II through whichand into the base extend vertically slidable rack members I2 fixed attheir upper ends to a clamping plate I3.

Extending longitudinally through the base l is a shaft I4, mounted insuitable bearings in the end walls, and provided with teeth at theportions adjacent racks I2 for engaging the teeth of the latter, so thatrotation of shaft I4 provides up and down motion of plate I3.

Rotation of the shaft I4 is accomplished by means of a lever I5 actingthrough self-locking means indicated as a whole at I6, the detailedconstruction of which is not being shown, but which provides for turningthe shaft and locking it automatically against reverse motion.

Since as stated above, the members I2 and I3 in heavy duty fixtures arequite heavy, a weight compensation means is shown as included in thestructure. This compensator is shown as a heavy helical spring 20, xedat one end 2I to shaft I4, and at its other end secured to a sleeve 22rotatably mounted on shaft I4.

This sleeve 22 is provided on its outer surface with worm teeth 23adapted to coact with a Worin 24 formed on a shaft 25 mounted insuitable bearings in the back and front walls of the base I Il, andextending through the latter to the outside, the projecting end beingsquared or otherwise shaped as at 26 to permit application of a suitablehandle (not shown) In mounting the shaft 25, it is preferred to provideits forward bearing in a bushing 21 fixed in the front wall of the baseas by a screw 28.

In operation, the fixture is adjusted so that the plate I3 is atapproximately the proper height for the work part to be operated, thetension of spring 20 is then adjusted to counterpoise the Weight of thevertically movable parts. Under such an adjustment, operation of thehand lever I5 provides a smooth easy action even in the largest andheaviest iixtures. The locking means I6 may be of any suitable form, butis preferably such as is shown in my previous U. Si. Patent No.2,171,458, issued August 29, 1939or No. 2,066,167, issued December 29,1936.

Now having described the invention and the preferred embodiment thereof,it is to be understood that said invention is to be limited, not to thespecific details herein set forth, but only by the scope of the claimswhich follow.

I claim:

1. A locking fixture including a base, a clamping plate located abovesaid base, rack members fixed to said plate and extending into saidbase, a shaft rotatably mounted in said base and provided with pinionscoacting with said rack members to move ysaid plate, means for rotatingand for locking said shaft in position, and means for counterbalancingthe weight of said plate and racks.

2. A locking iixture including a base, a clamping plate located abovesaid base, rack members fixed to said plate and extending into saidbase, a shaft rotatably mounted in said base and Tprovided with pinionscoacting with said rack members to move said plate, means for rotatingand for locking said shaft in position, and spring means adapted to actupon said shaft to provide a resilient resistance to its rotation towardclamping position.

3. A locking fixture including a base, a clamping plate located abovesaid base, rack members Xed to said plate and extending into said base,a shaft rotatably mounted in said base and provided with pinionscoacting withr said rack members to move said plate, means for rotatingand for locking said shaft in position, and means for counterbalancingthe weight of said plate and racks, said latter means consisting of aspring xed to said coacting with said shaft for counterbalancing the 10Weight of said plate and racks, means for xing one end of said spring tosaid shaft, and means for fixing the other end of said spring to saidbase and adjusting the tension thereof, said latter means consisting ofa sleeve rotatable upon said shaft and provided with worm gear teeth anda Worm shaft mounted in said base and coacting With said Worm gear onsaid sleeve.

GUY E. SWARTZ.

